Attaching Kit's Head
To attach the head to the body, I first imported Kit's head into the scene with her body. I resized her head to be the right size for her body before attaching it.
After resizing the head and neck, I looked at where the edges at the neck attached to the body and used multi-cut to continue those edges down the dress.
Then I used mudbox to see where there was problems in the topology and fixed any problems I found. There were some non-quads where the dress meets the legs, under the skirt. To fix these, I disconnected the legs so I could see the vertices under the skirt properly. I deleted some of the faces, then reorganised the vertices so none of them were overlapping and all the faces were quads. Then I use the extend to polygon and target weld tools to create faces under the skirt.
I did the same for the top of the legs and re-shaped them a bit before moving them back into place under the dress. I made her thighs a bit thicker and moved the skirt out a bit to accommodate them. I think her legs look better like this.